Underfloor air distribution (UFAD) is a method of delivering conditioned air inside offices and commercial buildings. UFAD is an alternative to ceiling-based heating, ventilation and air-conditioning (HVAC) methods. The open space between the sub-floor (usually a structural concrete slab) and the underside of a raised access floor is called the plenum or air handling space. UFAD systems use the plenum to deliver conditioned air into the occupied zones of the building. In a typical UFAD system, conditioned air is emitted by an air-handling unit (AHU), through the plenum and into workspaces via a variety of supply outlets (diffusers) or perforated floor tiles. The AHU is typically located in the plenum or is connected to the plenum via a minimum amount of ductwork. These supply outlets are usually located at floor level (most common), or as part of the furniture and partitions.
The underfloor plenum is formed by installation of a raised floor system. Usually this raised floor system consists of floor panels supported on pedestals and positioned above the concrete structural slab of the building. The conditioned air, being pressurized vis-à-vis the air above the plenum, typically flows freely in the plenum to the supply outlets or perforated tiles. The plenum thus provides a path for cooled air to travel from the AHU to the workspace. Access to the plenum can be achieved simply by removing one or more floor panels.
Equipment and data centers are also cooled using the plenum or underfloor air handling space. UFAD systems are particularly advantageous in light of the thermal cooling requirements of computer equipment and data centers. In fact, raised floors were developed in the 1950's and 1960's to facilitate the use and operation of mainframe computers, which required bottom air intake. However, equipment needs have changed in data centers over the past forty years, and servers and other equipment have replaced mainframes in the data center. The servers that have virtually replaced the mainframes can generate more heat than the mainframes in a more concentrated space. Current servers may produce up to six times more heat than the equipment they replace. Hence, data centers have greater cooling requirements than ever before.
Controlling high temperatures within data centers is very difficult and complex. Yet, keeping computers and data center equipment at the right temperature is critical for the life of the equipment. Such electronic equipment must be maintained in appropriate temperature environments subject to regulated rates of temperature change in order to maintain equipment reliability, abide electronic equipment warranty provisions and ascertain optimum energy usage. Achieving these requirements is an ever constant and evolving concern for the HVAC or IT professional due to the fact that computer and data processing equipment trend toward increasing the amount of power usage, and thus thermal output and cooling demand, over available space. Server manufacturers have used high output fans and enclosed chiller lines to control the high temperatures within data centers.
Another method of cooling electronic equipment environments and thus meet the thermal demands of computer equipment involves using a dedicated Computer Room Air Conditioner (CRAC) in association with a UFAD system. Electronic equipment, including computer systems, can be cooled using a pressured plenum under a raised floor. Powerful fans in the CRAC units draw in hot air exhausted by equipment in a data center. In a conventional CRAC arrangement, fans cool the hot air by forcing it through a liquid-to-air heat exchanger. With a CRAC-UFAD system, pressurized cooling air enters the plenum beneath the raised floor of a data center. Cooled air exits from conventional CRACs at a very high velocity. However, air velocities are low and constant after the air has traveled away from the CRAC a certain distance. The plenum provides a path for cooled air to travel from the CRAC to the data center. Cooled air is distributed to the equipment in the room by placing supply outlets in the form of floor tiles with perforations in close proximity to the cool air inlet vents of the equipment.
The plenum of today's building must now house building components and infrastructure beyond HVAC apparatus. By combining a building's HVAC system with its power, voice, and data cabling into the under floor plenum, significant improvements can be realized in terms of increased flexibility and reduced costs associated with reconfiguring building services. Consequently, under-floor systems, including UFAD systems, have become desirable in view of the fact that office buildings today have high office space reconfiguration rates resulting from tenant turnover and from the extensive and ever-changing information technology infrastructure and needs of business.
When cabling runways, copper and fiber distribution and power feeds for servers share plenum space with pressurized air, plenum airflow distribution becomes less predictable. Because rigid building structural members often define the lateral confines of the plenum, the configuration of a plenum cannot easily change to meet airflow demands. This is particularly a concern when dealing with a data center that was built many years ago, and has not been upgraded to meet current standards. Airflow is generally calculated to provide for sufficient cooling in newly constructed or recently updated data centers. Based upon such airflow calculations and measurements, perforated floor tiles and CRAC blower speeds are adjusted to achieve a desired airflow rate. However, after thermal demands are calculated and cooling parameters set, airflow rates are often unintentionally changed. Airflow rates often decrease due to the addition of cables and other items within the plenum. Modifications, such as holes, in the plenum can also cause drastic changes to the airflow rates by creating a low-resistance bypass for the high-pressure cooling air. Conditions and modifications within the plenum space and imprecise calculations and measurements often produce undesirable airflow distribution through the perforated floor tiles, which could, in turn, harm electronic equipment. There is thus a need in the art for a system that can direct airflow within a plenum and which can be easily installed, modified and removed.